The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) defines several tests for heating, ventilation, and air conditioning (HVAC) systems designed to mimic real-world conditions. The tests are specified in “AHRI 210/240-2008: 2008 Standard for Performance Rating of Unitary Air-Condition and Air-Source Heat Pump Equipment,” which is herein incorporated by reference. Of particular interest are two tests for two-speed or variable-speed compressors—the “A” test and the “F” test. The “A” test is a test conducted at a high compressor capacity with 95° F. air entering the outdoor unit, and the “F” test is a test conducted at a low compressor capacity with 67° F. air entering the outdoor unit. These tests are directed to so-called split HVAC systems comprising an indoor unit and an outdoor unit. These tests represent relatively extreme operating conditions for an HVAC cooling system.
One way to achieve a high Energy Efficiency Ratio (EER) and thereby affecting the Seasonal Energy Efficiency Ratio (SEER) rating for an HVAC system in the AHRI “A” test is to optimize charge for the “A” test. However, as a result of optimizing charge according to the “A” test, there may be a significant loss of subcooling in the AHRI “F” test. Conventionally, in order to remedy this, additional charge may be added to achieve sufficient subcooling for the “F” test. Adding this additional charge to provide sufficient performance for the “F” test presents a problem for the “A” test because charge is no longer optimized for the “A” test and the EER at the “A” test is accordingly decreased. The “A” and “F” tests can thus place competing demands on an HVAC system.